Which property should NOT be considered when comparing two synthetic fibers?

When comparing two synthetic fibers, the medullary index typically should not be considered because it is primarily a characteristic used for identifying and comparing natural fibers, particularly those derived from animal sources, like hair. The medullary index refers to the ratio of the diameter of the medulla, or central core, of a hair to the overall diameter of the hair itself. This attribute is not relevant to synthetic fibers, which do not possess a medulla in the same way natural fibers do.

In contrast, breaking strength, melting point, and fiber diameter are significant properties for synthetic fibers. Breaking strength refers to the amount of force required to break the fiber, which is crucial for understanding its durability and performance in various applications. Melting point is important as it indicates how the fiber will behave under heat, which is particularly relevant for applications involving exposure to high temperatures. Fiber diameter affects the texture and appearance of the synthetic material, influencing its use in textiles and composites. Thus, these three properties provide valuable information for comparing synthetic fibers, while the medullary index does not apply to them.